As I understand, these have expansion audio in the form of additional PCM (ADPCM?), supplied by the aforementioned chips. And they aren't supported in emulation. Having some audio recordings of them in action would be fantastic.

Well, for now you can check Youtube. There are some videos of hardware recordings.

M50805 is not entirely PCM. A colleague, hopefully, will be able to extract the PARCOR data in the coming weeks.

Another friend and I are in the process of attaching the 7756 and M50805 to a TNS* NSF cart that we will be programming custom NSFs for; which should control the audio outputs. He should be able to make recordings. Ultimately, we would like to have the data dumped.

To repeat what's been said in the past: if we change the clock of the µPD775x part, we should be able to get enough more data such that we can generate a perfect 9-bit back-translation of the DAC values. But this recording I found to be just a little too noisy for me to be confident I could calculate that exact values used in the DAC.

The datasheet for the part implies each recording inside the IC can choose between dividers of 80, 104 (edit: determined from spectrogram of above recording), or 128 to generate the sample clock (640kHz→8, 6.2, or 5kHz). Although normal 44kHz sound card sampling "should" be enough, I'd really be happier with a larger amount of oversampling ... and ideally using a sampler that doesn't have a highpass filter on its input.

Last edited by lidnariq on Fri Jun 23, 2017 2:38 pm, edited 2 times in total.

Well, for now you can check Youtube. There are some videos of hardware recordings.

M50805 is not entirely PCM. A colleague, hopefully, will be able to extract the PARCOR data in the coming weeks.

Another friend and I are in the process of attaching the 7756 and M50805 to a TNS* NSF cart that we will be programming custom NSFs for; which should control the audio outputs. He should be able to make recordings. Ultimately, we would like to have the data dumped.

That would be fantastic! Looking forward to your findings. Amazing work, and thank you for trying to shed light on this.

Another friend and I are in the process of attaching the 7756 and M50805 to a TNS* NSF cart that we will be programming custom NSFs for; which should control the audio outputs.

I just took a look at the JF-24A (SS88006 using) board and noticed that our previous documentation was at least partly wrong. These boards definitely connect CPU D7...D3 (and very likely D2) to µPD775x I5..I0

Given previous muddied documentation it seems very likely that D1 and D0 are latched by the SS88006 and connected to µPD775x /START and /RESET respectively. But I can't verify this.

I feel it is somewhat debatable whether the discrete sound chips or the US versions playing of samples sounds clearer, but the sound effects for the Jaleco baseball and tennis games are much improved over their NES counterparts.

To repeat what's been said in the past: if we change the clock of the µPD775x part, we should be able to get enough more data such that we can generate a perfect 9-bit back-translation of the DAC values. But this recording I found to be just a little too noisy for me to be confident I could calculate that exact values used in the DAC.

The datasheet for the part implies each recording inside the IC can choose between dividers of 80, 104 (edit: determined from spectrogram of above recording), or 128 to generate the sample clock (640kHz→8, 6.2, or 5kHz). Although normal 44kHz sound card sampling "should" be enough, I'd really be happier with a larger amount of oversampling ... and ideally using a sampler that doesn't have a highpass filter on its input.

According to the datasheet, the sample data could just be dumped with "verify" mode too if the chip were pulled, eh?

Oh, YES! I remember reading that. I guess I'll talk to ImATrackMan to see if he can lower the clock of some of the 7756 cart I gave him so he can record some sample data for you; if you're up to the task of converting it to 9-bit?

I'm certainly up for giving it a shot. I don't know how much head room below the nominal 640kHz will be useful—obviously it's partially a function of the sample rate and highpass/lowpass corners of the recording sound card also.

The fun bit is gonna be unboiling the egg and turning the recovered 12?-bit pcm data back into the 4-bit-per-sample source adpcm data from the 7756c mask rom. That's actually possibly doable, since theres only 16 possibilities per sample and you can do analysis-by-synthesis to find best fit for each one.

Or someone could donate 7756 carts for decap, sean riddle has been doing some amazing stuff with game&watch game MCUs recently, so it might be possible to optically read 7756 rom, unless they used implant rom for it...

LN

EDIT: But that m50805 REALLY interests me as well, that's i believe in the same series of LPC/PARCOR chips as used by the original "talking" version of nintendo's arcade game "radar scope".I'd honestly love to see one of those chips decapped so I can make sure the LPC tables in mame are correct, for synthesis.

_________________"When life gives you zombies... *CHA-CHIK!* ...you make zombie-ade!"

One of the random things I find interesting is that the implementation of the µPD7759 in MAME only mentions the 4bit-per-sample ADPCM.

And yet, the datasheet for the µPD775[5-8] says "bit rates from 10kbit/s to 32kbit/s", implying that there's a 2bit/sample ADPCM mode... At least, I think they're implying that instead of just referring to repeat mode. They do explicitly call out silence padding separately.

MAME's µPD7759 implementation also implies a wide range of possible sample rates, ranging anywhere from 160kHz down to 2.5kHz (I think? Assuming 640kHz÷4÷(F+1)), and can switch during in the middle of playback.

Lord Nightmare: The person in question also has the cart. If you wish to contact him, he may be able to help. I'm not concerned with the state of return of the cart; as long as it's dumped and emulatable.

With some redaction, here are the WAV files dumped from the chip by Sean and some information:

"It works as described in the datasheet; every 64 clocks (100uS at 640kHz), DA0 or DA1 goes low for 0 to 63 clocks. I exported the dump and combined the two PWM signals for each sound into a single 7-bit signed file, then used Audacity to convert those into WAV format:"

We're still in the process of troubleshooting and finding methods to find the encoded data.

Removed the attachment so that bad files are not distributed.

Last edited by B00daW on Mon Jun 26, 2017 5:43 pm, edited 2 times in total.

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